Flexible diaphragm for fuel pumps and the like and method of forming the same



Jan. 10, 1956 H. L. ASP ET AL 1 2,730,131

PHRAGM FOR FUEL PUMPS FLEXIBLE DIA AND THE LIKE AND METHOD OF MING THE SAME Filed Jan. 1955 INVENTOR.

HOWARD L. PAUL 'r. HA

United States Patent (3 FLEXIBLE DIAPHRAGM FOR FUEL PUMPS AND THE LIKE AND METHOD OF FORMING THE SAME Howard L. Asp, Evanston, and Paul T. Haaka, Park Ridge, Ill., assignors to Crane Packing Company, Chicago, 111., a corporation of Illinois Application January 2, 1953, Serial No. 3255382 5 Claims. (Cl. 137-793) The present invention relates to flexible diaphragms and more particularly to a diaphragm of the type which has a central body portion which moves in a direction transversely of the general plane of the diaphragm and relative ot the peripheral portion thereof. The invention is also concerned with a novel method of forming such diaphragms.

Diaphragms of the type outlined above will be found useful in connection with fuel pumps for automotive or Diesel use, as well as in connection with a large variety of other instrumentalities which depend for their operation upon the use of a flexible member of this character. Among such instrumentalities are pressure regulators which are employed for controlling a flow of a liquid or gaseous medium from a high pressure area to a low pressure area; valve constructions; airbrake mechanisms; pressure operated electrical circuit making and breaking apparatus, and many other constructions or assemblies where the flexible member is generally known under the general characterizing term of pump diaphragm regardless of whether it is primarily designed for use in connectiori with a pump or only in a generally related manner.

Diaphragms constructed in accordance with the principles of the present invention contemplate the employment as an essential part thereof, if not as the entire diaphragm, a suitable flexible impervious material or compound which will satisfy all of the requirements of a pump diaphragm, particularly with respect to flexibility.

Among the compounds contemplated as a base material for construction of the present diaphragm is a polytetrafluoroethylene polymer manufactured by E. I. du Pont de Nemours 8: Company under the trade-name Teflon. This material is characterized by its chemical inertness through a range of temperatures extending from extremely low temperatures up to approximately 570 F. Teflon is insoluble in all known chemicals and no reaction has been noted with any chemicals including the most destructive type such as the halogenated hydro-carbons,

chlorosulfonic acid acetyl chloride, boron trifluoride and other high boiling point solvents at their boiling points.

Such chemical inertness of Teflon would ordinarily point the way toward its ideal use as a pump diaphragm for fuel pumps or for other hydraulic devices such as valves, particularly where oils or corrosive acids are encountered. However, while this material has adequate toughness, and is possessed of good tensile strength, as well as of excellent abrasive and frictional qualities, it lacks the resiliency necessary to insure ease of flexing when employed as a diaphragm, particularly at the thicknesses demanded by the ordinary engineering exigencies of fairly large installations.

The present invention is designed to overcome the above noted physical limitations that are attendant upon the use of Teflon as a diaphragm material, as well as end, the invention contemplates the provision of a novel diaphragm, preferably formed entirely of Teflon which ,vention have been shown.

2,730,131 patented Jan. 10, 1956 is so constructed as to have relatively movable central and peripheral regions which are connected together by a multi-layer intermediate ring-like area or portion of greater flexibility than the remaining portions of the diaphragm and in which the layers thereof are capable of independent flexing so as to greatly increase the sensitivity of the diaphragm as a whole.

The diaphragm, in one form thereof is formed of a single piece of the Teflon or other material with solid relatively movable inner central and outer peripheral regions respectively, connected together by the intermediate multi-layer flexible region. In another form, the diaphragm is of similar design with strips of foil or other separator material interposed between the layers of the intermediate region. In yet another form of the invention the diaphragm may have a solid central region and .the remainder thereof, including the peripheral region,

may be laminated.

In each of the above contemplated forms of the diaphragm, different methods of manufacture may be resorted to and, among these methods, at least one of them is regarded as being novel and within the scope of the present invention.

The provision of a flexible diaphragm of the character briefly outlined above being among the principal objects of the present invention, other objects and advantages will become more readily apparent as the following description ensues.

In the accompanying single sheet of drawings forming a part of this specification several embodiments of the in- In these drawings:

Fig. l is a plan view of one form of the improved pump diaphragm constructed in accordance with the principles of the present invention. In this view, a subsurface cut has been made in the front face of the diaphragm to more clearly reveal the nature of the invention.

Fig. 2 is a sectional view taken substantially along the line 2-2 of Fig. 1.

Figs. 3 and 4 are sectional views similar to Fig. 2 taken through slightly modified forms of diaphragm.

Fig. 5 is a vertical sectional view, somewhat schematic in its representation, of a mold which may be employed to perform the final sealing step in the manufacture of the diaphragm of Fig. 1.

Fig. 6 is a sectional view similar to Fig. 5 showing a mold which may be employed to perform the final sealing step in the manufacture of the diaphragm of Fig. 4 and Fig. 7 is a fragmentary side elevational view, schematic in its representation, showing certain steps that are performed in the construction of the diaphragm illustrated in Fig. l.

Referring now to the drawings in detail and in particularto Figs. 1 and 2 wherein one form of flexible pump diaphragm constructed in accordance with the principles of the present invention has been shown. The diaphragm is in the form of a single piece of flexible impervious material of circular disc-like configuration including a flat peripheral rim portion 10, a slightly offset central portion 12 and a frusto-conical connection portion 14 of wide taper. The offset portion 12 includes a solid hub 16 and the peripheral portion 11 is in the form of a solid ring of the material of which the diaphragm is formed, the hub 16 and rim- 11 being integrally joined by separate layers or laminations 18 of the material. The diaphragm is provided with the usual central attachment hole 20 which passes centrally through the hub 16 and the rim portion 11 is provided with the usual spaced bolt holes 22. It is to be noted that the medial laminated portion of the diaphragm extends from the peripheral edge of the hub 16 to and beyond a peripheral edge of the offset portion 12 and through the frusto-conical connection portion 14 to the inner edge of the solid rim portion 11.

In manufacturing diaphragms such as are shown in Figs. 1 and. 2, a. cylinder of. the. moldedmaterial isfirst provided in any suitable manner, as for example by a molding operation with an inside diameter equal to the diameter 05 the bolt hole and with an outs-id'e diameter' equal to thediametrical extent of the: completed diaphragm. Sucha cylinder isxshown at2'4 in Fig; 7'. The cylinder is then mounted ina-rotating chuck- 26'and slicing operations are-performed upon it to-ccnsecutively produce a series of the diaphragms. Utilizing a suitable cutter 28, the material of the cylinder is sliced inwardly adjacent the free end thereof to the periphery of the hub, the thicknessof'theslice being equal to thethickness of one of the laminations 18. The cutting tool is then withdrawn and additional slices are made in the cylinder until the requisite number of laminations 118 have been formed. The last'slice made upon the cylinder to produce a-- si'nglediaphragm is carriedthrough the cylinder to completion so that a diaphragm blank such as the one shown at 29 in Figs. 5 and- 7 is formed and separated from-the remainder of= the-body portion of the cylinder. These slicing operations are repeated until the-cylinder has been divided in its entirety into a number of the blanks 29. The severed units 29' areremoved from the chuck 26 and the bolt holes-22 are formed therein in any suitable manner, as forexample-by a punching operation.

In order to seal the peripheral regions oftheindividual layers thus created in themarginalregions ofeach diaphragm blank, the blank is operated upon by a molding apparatus such as that shown in Fig. 5. This apparatus includes upper and lower dies 30 and 32 respectively,

together with suitable means (not shown) for moving the dies relative-to each other. 7

The upper dieStl includes a central section 34- and a concentric surrounding section 36, the two sections being separated by a heatinsulating member 38 of tubular configuration. The lower die32 is of similar design and includes a centralsection 40 and a concentric'outer section 42 which is separated from the central section 40 by a tubular insulating member 44. The composite lower die- 32 is provided witha shallow circular'recess or depression 46 and the upper composite die'30 is-provided with a-cooperating circular protuberance-48, the depres sion 46 and protuberance4$ cooperating witheach'other' toprovide the offset portion 12 ofthe completed diaphragm as shown in Fig. 2. The die section 34 is'provided with a centering holeSll while the cooperating die section 40 is provided with a centering pin 52in registry withthe hole 50.

The outer upper and lower die sections 36 and 42 respectively are adapted to beheated in-any suitable manner; as for example by conventional band heaters 54.

Whentheindividual diaphragm blanks 24-are operated upon by the molding structure Fig. 5, it will be-seen that the layers or laminations of the blank in the peripheral regions thereof will be heat sealed together to provide the peripheral ring portion- 16 of the diaphragm" shown in-Fig. 2. The degreeof heat employed and the pressure involved will, of course, varytosuit the requirements of these diaphragm materials and for purposes of illustrations utilizing Teflon as the material of the diaphragm, the sections 36 and 42 may be brought to a temperature of 750 F. orthereabouts and the pressure maintained for approximately 20 seconds, after which the mold sections may be separated and thecompleteddiaphragm stripped therefrom.

Referringnow to Fig. 3 it willbe seen that the diaphragm illustrated therein is similartothat shown in Fig. 2. The principal difference is that the marginal region of'the diaphragm is notheat seaiedand the various laminationsassociatedwith the diaphragm remain free of-each other in this'marginal region. Fig. 3 may :be formed in-a manner substantially identical with theformation ofthe diaphragm of Fig. Z'but-inthis latterfornr of diaphragm'theheat sealing operation is 'lhe diaphragmof omitted so that the diaphragm exists as a completed article as soon asit hasbeensevered from the Teflon cylinder 24. Utilizing similar reference numerals, the diaphragm of Fig. 3 thus consists of the solid central hub portion 16a and a series of outer surrounding separated layers 18a of the materiaLwhich remain separated from the periphery of the hub portion 161: completely to the periphery of the diaphragm. For purposes ofiillustrationg the various layers 18a at the right hand side of. Fig; 3

of material designated at 60, 62 and 64. respectively.

These layers are heat sealed together to provide a central hub portion 16b which in effect constitutes a homogeneous central hub. The various layers 60, 62, and 64 are also heat sealed at their peripheral region to provide an outer rim portion 10b which in efi'ect'. is. uniformly solid, the two solid unbroken portions 161: and- 10b being interconnected by the separated laminations 18b. If desired, relatively thin fiat rings 68' of metal foil which maybe of aluminum are interposed. between the separated layers 18b; These rings do not detract from the flexibility of. the diaphragm as a whole and they serve to effect, sharp lines of division between theunsealed and heat-sealed portions of the diaphragm respectively: The metal foil rings 68', in' addition to their separating function, also serve as anti-friction members which permit the various laminations or layers of the Teflon material to slide upon one another. thus enhancing the fiexibility'of the medial regions of'the' diaphragm. Since the metal foil elements are. relatively thin and yieldable, they cannot be regarded as reinforcing members and their true functions are as separators andanti-friction members'as stated above.

In the formation of the diaphragm-of Fig. 4, a molding apparatus such ashas been illustrated in Fig. 6 is employed. This apparatus is similar to-the apparatus shown in Fig. 5 and includes upper and lower die assemblies and 81 respectively.

Theupper die 80 includes a central section 82 and concentric-outer ring-likesections 84- and 86'. Thecentral core section 82 is provided with a centering hole 88. The cooperating mating lower die- 81 is similarly formed with a central section 90- and concentricsur= rounding ring sections 92 and 94. The coresection 90 is provided with a centering pin 96 in registry-with the centering hole 88.

The-central core sections 82 and 90 are adapted to be heated in any-suitable manner; as for exampleby surrounding band heaters 98 and theouter cooperating mold sections 86 and 94 are adapted to be similarly heated by band heaters 99 as shown. The intermediate cooperating mold sections 84 and 92' remain unheated; insulating rings or cylinders 100 and'102 serve to separate the intermediate mold sections 84 and 92 from the central and outer sections 82; 86 and 90',- 94 respectively;

The composite mold section 81- is provided with a shallow circular depression or recess 104 and'the composite mold 80' is provided with a complementary circular protuberance 168, which recess and protuberance" cooperate with each other to provide the offset. inter; mediate region 12b of the completed diaphragm of'Fig. 4. In the molding operation, the. heated portions of the dies may be maintained ata temperature of; 750"Fl and the duration of" the moldingoperation; may be 20 seconds. Itwill be understood, however,,that, thedura; tion of moldingtime and the degree of heat applied may be varied in. accordance withtlie thickness off'th'e various layers to be heat sealed and in accordance with the combined thicknesses of these layers.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification, nor is it to be limited to the specific process described herein. Various changes in the details of construction and in the process involved may be resorted to without departing from the spirit of the invention. For example, while in each of the diaphragms shown, three layers or laminations are illustrated in the central regions of the diaphragm, it will be understood that a greater or lesser number of such laminations may be utilized if desired. Similarly, the temperatures and pressures referred to are only exemplary and for different sizes and shapes of diaphragms, as well as for diaphragms which are formed of different materials, these temperatures and pressures will be varied so as to produce the desired heat sealing of the laminations at the periphery and, if desired, in the central regions of the diaphragm. Only insofar as the invention has been particularly pointed out in the accompanying claims is the same to be limited.

What is claimed:

1. A flexible pump diaphragm of the character described comprising a unitary disc-like member of appropriate configuration and of a homogeneous flexible material including a solid unbroken central hub portion of predetermined uniform thickness, a solid unbroken continuous outer peripheral portion of the same predetermined uniform thickness, and an intermediate portion connecting said hub and peripheral portions, said intermediate portion comprising a plurality of layers of the homogeneous flexible material, each layer being in the form of an unbroken continuous flexible ring having its inner margin integrally joined to the periphery of said hub portion and its outer margin integrally joined to the inner margin of the outer peripheral portion, the opposite faces of said diaphragm being free of radial and circumferential seams and joints and presenting smooth unbroken surfaces, and a flat continuous ringlike member of metal foil interposed between the adjacent superimposed layers of the homogeneous flexible material and substantially filling the space existing therebetween.

2. A flexible pump diaphragm as defined in claim 1 in which the central hub portion and the outer peripheral portion are offset from each other and in which the layers of the intermediate portion are contained in part in the general plane of said hub portion.

3. A flexible pump diaphragm as defined in claim 1 in which the central hub portion and the outer peripheral portion are offset from each other and are connected together by an inclined medial portion and in which the layers of the intermediate portion are wholly contained in the general plane of said hub portion and in the inclined medial portion.

4. The method of forming a series of flexible pump diaphragms from cylindrical flexible stock which comprises slitting the stock transversely inwardly from the cylindrical surface thereof along closely spaced parallel planes a predetermined distance to provide a series of ring-like layers of the material of the stock in the outer regions of the stock while leaving a solid central hub portion, and severing the thus partially formed diaphragms from each other by effecting a series of transverse cuts completely through the stock between adjacent partially formed diaphragms.

5. The method of forming a series of flexible pump diaphragms from cylindrical flexible stock which comprises slitting the stock transversely inwardly from the cylindrical surface thereof along closely spaced parallel planes a predetermined distance to provide a series of ring-like layers of the material of the stock in the outer regions of the stock while leaving a solid central hub portion, severing the thus partially formed diaphragms from each other by effecting a series of transverse cuts completely through the stock between adjacent partially formed diaphragms, and thereafter individually heatsealing the peripheral regions of the diaphragms to secure the various layers thereof together.

References Cited in the file of this patent UNITED STATES PATENTS 356,997 Gil Feb. 1, 1887 1,145,671 Butcher July 6, 1915 1,213,051 Wickes Jan. 16, 1917 1,386,722 Mather Aug. 9, 1921 1,604,925 Macdonald Oct. 26, 1926 1,695,534 Carter Dec. 18, 1928 1,742,398 Kelley Ian. 7, 1930 1,850,684 Nathan Mar. 22, 1932 1,902,323 De Monge Mar. 21, 1933 2,033,354 Pennington Mar. 10, 1936 2,235,872 Ford Mar. 25, 1941 2,304,618 Williams Dec. 8, 1942 2,646,077 Whitney July 21, 1953 FOREIGN PATENTS 27,009 Great Britain of 1896 OTHER REFERENCES Modern Plastics, November 1947, pp. 108-109. 

